Cathode ray tube



Aug. 13, 1940. F. scHRO'rER CATHODE RAY TUBE Filed Aug. 5, 1936 3 QE SERNQ QERQWNQQQ QR INVENTOR FRITZ SCHROTER BY lg g ATTORNEY Patented Aug. 13, 1940 are? rENr ores cArrnopE RAY TUBE lFritz Schriiter, Berlin, Germany, assignor to TelefunkennGesellschaft fiir Drahtlose Teletion of Germany graphic m. b. IL, Berlin, Germany, a corpora- Application August 5, 1936, Serial No. 94,38

in Gnarimmy August 5, 1935 i 7 Claims. (c1. ids-7.2)

My invention relates broadly to scanning devices for television purposes and more particularly to a cathode ray type of scanning appa- U ratus. In my previous application, S. N. 32,768 filed July 23, 1935 andntitled Television scanner there is described the combination of a single line cathode ray scanning device associated with an optical arrangement by means of which the optical image to be transmitted is displaced across the scanning line in the direction of the second analyzingcocrdinate by means, for instance, of a mirror :wheel.

The present arrangement has for itscbject to eliminate all inconvenient mechanical accessory means and to this end the original image is transformed in two dimensions into an electron image and the electron image is drawn a line at a time across'a series oielectrodes, which are linearly arranged with respect to each other, andthe cathode ray beam developed in the tube scans the single line of electrodes on the'side opposite that on which 'the lines of the electron image fall.

My device in general operates in the following mannerzQ-the optical image to be transmitted is first transformed into an electron image and by means of electron optical means, the electron image is greatly enlarged in size. The enlarged electron image is then brought into contact with a set of individual cells which are linearly arranged so'as to contact a single line of the electron image. The image is then brought into contact with the line of cells; one line at a time, and each individual line charges the cells with charges corresponding on each cell to the electron value of the line at that point. This single line of the electron image is scanned by means of a cathode ray and a secondary emission is developed therefrom, which is proportional to the charge on each' cell. After the single line has been scanned, the electron image may be moved dowri' one line, where it again charges the cells and the steps. as outlined before, are repeated.

5 My invention will best be understood by ref erence to the figure which shows an embodiment of -my invention. I

Referring to the figure, I is the optical view which is to be transmitted by television and 2 50 is an objective lens reproducing the optical im'- age on a homogeneous surface 3 which is photoelectrically sensitive, the optical image having passed through the transparent front wall of the cathode ray tube Q and through a trans- .55 parent conducting layer. The electron image formed by 3 is then influenced by a magnet coil excited with a direct current which acts as a reproducing lens This coil produces in the plane of a cell line 8 an enlarged electron image of the object I which is to be transmitted. For the sake of simplicity, the turning of the electron image by the magnetic lens is not considjacent the cell line 8 is a common conductor 9 m arranged so as to form a capacitive element with each of the cells 8 and is'so arranged as to be out of reach of the reproducing electrons, as well as the scanning electrodes. This may be ac complishedby a physical postioning and shielding. In the opposite end of the cathode ray tube, from the end in which the optical image entered, there is developed acathode ray beam which may be deflected by well known deflection arrangements. For the sake of simplicity, 2 I have indicated one magnetic coil [5. However, it is understood that electrostatic means may be used as well as a dual magnet coil arrangement. An anodic layer Hi is provided which may be joined at the end remote from the cathode ray generating means by means of a mesh I3 of finewires.

The line movement of the ray may be obtained by means of a magnetic field produced by relaxation current which is established by the coils 3 IS. The movement of the cathode ray across the side of the cell line 8, which is remote from the electron image, will return the cells to an equilibrium state and will cause the production of secondary emission of a value which is dependto ent on the charge on the cell as well as the acceleration'of the beam. This secondary emission is collected by the mesh member 03 and produces a varying potential across the resistor ID. This varying potential may then be used to modulate the transmission apparatus in well known fashion. v

So far there has been explained the scanning of one line of the image. After scanning the single line, the electron image may be moved with respect to the cell line 8 by a distance corresponding toone line of the image by means of a coil pair I. The coil pair I is fed with a relaxation current of the frequency corresponding to the picture frequency and naturally moves the 5 electron image in a direction at right angles to the line 8. As a result thereof, the various lines of the image act in succession upon 8 in accordance with the linear distribution of their electron density so that all picture points will be evacuated in proper sequence. In this manner, the cathode ray scanning beam is moved only in one direction, that is, along a single coordinate, which is at right angles to the movement of the electron image.

Where interlaced scanning is desirable, the electron image is moved by the coil 7 a space of more than one single line or as it is generally termed, more than the width of a single elemental picture strip.

For more effective scanning performance, the individual cells 8 can be so constructed and biased that the image electrons impinging thereon, multiply through secondary emission the accumulated charges. For instance, the surface of the cells 8 exposed to the image electrons may be coated with caesium or other electro-positive material in known manner for the production of photocells, and thereby a multiplication up to about fiv-e times the impinging electron quan-- tity is obtained. The most favorable potential value for utilizing the secondary emission can be given the cells 8 by properly choosing the potential of the accelerating anode M of the tube.

On the other hand, it is also possible to merely suppress secondary emission on the surface of the individual cells whichis struck by the image electrons. This may be accomplished by suit ably covering that face of the. cell With a'carbonaceous material. The front of the cell may be covered with the carbonaceous material as hereinbefore stated and the surface of the cells, remote from the electron image, may be coated with a material which has a high secondary emission characteristic. In this manner,-there will be obtained a reduced inner resistance of the cells for the compensation of the stored charges. The important advantage of the described single line arrangement resides in the easy assembly of the cell row line- 8 in forms susceptible of wide variations. Theqrequired insulation resistance of the cells relativeto each other can be easily attained.

It is possible to construct the individual cells of the scanning line as insulated electrostatic miniature cages and a high multiplication of the entering charge in each cage may be attained.

What I claim is:

1. In television apparatus for transmitting signals representative of an optical image, means for converting the optical imageinto an electron image, electron optical means for magnifying the electron image, a plurality of discrete cells, a conducting member adapted to form with said cells a plurality of electrical storage means, the cells being arranged to embrace a single elemental strip of the electron image, electrical? means transmission.

2. In a television transmitting apparatus for transmitting an optical image, means for.con-

verting the optical image into an electron image, electron optical means for magnifying said electron image, a plurality of discrete cells placed in a linear fashion facing the electron image, a common conducting member adapted to form with said cells a plurality of electrical storage means, electrical means for projecting the electron image one line at atime on one side of the line of cells and moving the electron image linearly in a direction at right angles to the line of discrete cells to produce electrical charges thereon, cathode ray producing means, means for moving the cathode ray on the side opposite the electron image across the line of cells in a direction perpendicular to the linear movement of the electron image in order to return each cell to an equilibrium state after accumulation of a charge for one picture element during a time interval between two successive passages of the cathode ray thereover, means for collecting the secondary emission occasioned by the impinging of the cathode ray on the line of cells, and means for modulating a carrier wave in accordance with the variations in the collected secondary emission.

3. In a television transmitting apparatus for transmitting an optical image, means for converting the optical image into an electron image, electron optical means for magnifying said electron image, a plurality of discrete cells placed in a linear fashion facing the electron image and a carbonaceous deposit on the side of the cell facing the electron image in order to reduce secondary emission from that side, a common conducting member adapted to form with said cells a plurality of electrical storage means, electrical means for projecting the electron image one line at a time on one side of the line of cells and moving the electron image linearly in a direction at right angles to the line of discrete cells to produce electrical charges thereon, cathode ray producing means, means for moving the cathode ray on the side opposite the electron image across the line of cells in a direction perpendicular to the linear movement of the electron image in order to return each cell to an equilibrium state after accumulation of a charge for one picture-element during a time interval between two successive passages of the cathode ray thereover, means for collecting the secondary emission occasioned by the impinging of the cathode ray on the line of cells, and means for modulating a carrier wave in accordance with the variations in the collected secondary emission.

4. In a television transmitting apparatus for transmitting an optical image, means for converting the optical image into an electron image, electron optical means for magnifying said electron image, a plurality of discrete cells placed in a linear fashion facing the electron image, each of said cells bearing a deposit of material having high secondary emission properties on the side facing away from the electron image, a common conducting member adapted to form with said cells a plurality of electrical storage means, electrical means for projecting the electron image one line at a time on one side of the line of cells and moving the electron image linearly in a direction at right angles to the line of discrete cells to produce electrical charges thereon, cathode ray producing means, means for moving the cathode ray on the side opposite the electron image across the line of cells in a direction perpendicular to the linear movement of the electron image in order to return each cell to an equilibrium state after accumulation of a charge for one picture element during a time interval between two successive passages of the cathode ray thereover, means for collecting the secondary emission occasioned by the impinging of the cathode ray on the line of cells, and means for modulating a carrier wave in accordance with the variations in the collected secondary emission.

5. In a television transmitting apparatus for transmitting an optical image, means for converting the optical image into an electron image, electron optical means for magnifying said electron image, a plurality of discrete cells placed in a linear fashion facing the electron image, said cells having a carbon deposit on the face of each cell facing the electron image and a deposit of a material having a low electron retention value on the face facing away from the electron image, a common conducting member adapted to form with said cells a plurality of electrical storage means, electrical means for projecting the electron image one line at a time on one side of the line of cells and moving the electron image linearly in a direction at right angles to the line of discrete cells to produce electrical charges there-,

on, cathode ray producing means, means for moving the cathode ray on the side opposite the electron image across the line of cells in a direction perpendicular to the linear movement of the electron image in order to return each cell to an equilibrium state after accumulation of a charge for one picture element during a time interval between two successive passages of the cathode ray thereover, means for collecting the secondary emission occasioned by the impinging of the cathode my on the line of cells, and means for modulating a carrier wave in accordance with the variations in the collected secondary emis- 51011. i 1

6. The method of scanning an optical image which comprises the steps of converting the optical image into an electron image, electro optically magnifying said electron image, storing an electric charge which is representative of the value of each element of the image for a single line of the image, electrically returning each charge to an equilibrium state subsequent to the accumulation of each charge thereon producing secondary electron emission upon the return of each stored charge to equilibrium value, collecting the secondarily emitted electrons produced, electrically moving the electron image in a direction transverse to the direction of scanning the charge image so as to store a single line of the image at any one time, repeating the steps set forth after the conversion of the optical image into an electron image.

7. The method of scanning an optical image which comprises the steps of converting the optical image into an electron image, electron optically magnifying the size of the electron image, storing an electric charge which is representative of the value of each element of the image for a single line of the image, electrically returning each charge to an equilibrium state subsequent to the accumulation of each charge thereon producing secondary electron emission upon the return of each stored charge to equilibrium value, collecting the secondarily emitted electrons produced, electrically moving the electron image in a direction transverse to the direction of scanning the charge image a space of one line, repeating the steps set forth after the magnification of the electron image.

FRITZ soHRoTER. 

